The invention relates to a bipolar stepping motor, especially for use as a watch drive, and particularly concerns a motor having a single stator sheet, a rotor, an air gap between the two which is not uniform, and a coil partially surrounding the stator sheet.
A stepping motor of the previously described type has already become known from the addition to French patent 73,591 (FIG. 1 thereof). The stator shown there carries on its straight connecting element a coil between the legs of the stator. This connecting element passes over at a right angle into straight partial pieces of the stator legs. Even though the known motor is shown as consisting of a single stator part in the above-mentioned patent, in practice nevertheless these stators hitherto have been composed of several partial pieces in order to be able to wind the straight connecting piece in a simple manner. The connecting piece was then customarily rivetted together with the straight partial pieces of the stator legs. In such stators, for one thing, the losses due to scatter are quite considerable because of the partially rectangular configuration. For another thing, the body of the coil, and thus the winding space, is being dimensioned at an optimally large dimension. Thus the degree of effectiveness is not optimal either.
It is an object of the invention, starting out from the previously designated status of the prior art, to create a bipolar stepping motor which, based on a consideraly improved degree of effectiveness, has a higher torque.